Coin operated devices have become very popular. Some examples of such are coin operated pay telephones, coin operated laundry machines, vending machines, parking meters, etc. One problem associated with such coin operated machines is that a wide variety of slugs have been developed in order to try to obtain products or services fraudulently from these coin operated machines without having to pay for the products or services.
In the past, it has been common to provide a mechanical mechanism for sorting and discriminating coins deposited in the coin operated device and for rejecting slugs. These mechanical discriminators typically have multiple passageways into which coins are directed depending upon their size. In known mechanical discriminators the mechanisms check both the diameter of the coin and its thickness. Unfortunately, the mechanical discriminators tend to be rather complex and are very prone to jamming. This requires a high number of service calls, at substantial expense. Also, use of these mechanical discriminators tends to be limited to certain predefined coin types and, once mechanical discriminators are made, they are not easily retrofitted to discriminate a new coin type. Also, because coin denominations take different coin paths within the mechanical discriminator, the limited space inside the discriminator tends to limit the variety of coins that can be discriminated thereby.
More recently, electronic coin discriminators have been developed. For example, U.S. Pat. No. 4,089,400 of Gregory, Jr. relates to a coin testing device in which multiple photo sensors (arrays thereof) are aligned along a coin path for determining the diameter of a coin passed therethrough. Gregory, Jr. describes that for each denomination to be tested, a separate series of photo sensor arrays is provided. This is necessary because each individual photo sensor in the array is simply providing information about whether it is covered or uncovered. Thus, to provide some modest level of precision in the measurement, a large number of photo sensor arrays are required for each denomination to be checked. In addition to Gregory, Jr., the following U.S. Pat. Nos. also disclose the use of an array of photo sensors: 4,267,916 of Black, et al.; 4,577,744 of Doucet; 4,667,093 of McDonald; 4,474,281 of Roberts, et al.; and, 4,076,414 of Kimoto.
In contrast to the use of one or more arrays of photo sensors, it has become known in the art to use a single photo sensor to measure diameter. For example, U.S. Pat. No. 4,531,625 of Yonekura. et al. relates to a coin diameter determining device in which a single light source is associated with a collimating lens to provide a collimated source of light. The diameter is then measured using multiple image sensors or photodetectors. While Yonekura et al. shows the use of a single lens arrangement, U.S. Pat. No. 4,848,556 of Shaw, et al. discloses the use of a dual lens arrangement so that a single infrared LED emitter can be used in conjunction with a single photodiode. According to the '556 patent, a collimating lens is placed between the LED emitter and the coin to be measured to collimate the light from the LED emitter. Another lens, this one a converging lens, is placed between the coin and the further diode. Other U.S. patents disclosing the use of a lens in connection with measuring the diameter of a coin include U.S. Pat. No. 5,033,602 of Saarinen, et al. and U.S. Pat. No. 5,033,603 of Kai, et al. One particular difficulty with the use of lenses is that they require precise orientation, installation, and calibration. Unfortunately, this makes it difficult to quickly and easily produce a repeatable product.
In addition to measuring the diameter of a coin, it has also been somewhat known in the art to measure the thickness of a coin passing through a discriminator. The mechanical discriminators mentioned above oftentimes are provided with means for determining the thickness of a coin, such as pincers or feelers or some other way of determining thickness. In the non-mechanical discriminators, it has been common to use some sort of mechanical or electromechanical device to determine the thickness of a coin. For example, in U.S. Pat. No. 4,577,744 of Doucet the discriminator uses stairstepped ramps or inclined ramps to change the position of a coin in the coin path according to the thickness of the coin. By noting which photo sensors of the array are covered and uncovered, and not just how many are covered or uncovered, the apparatus according to the '744 patent is able to discern the thickness of the coin passing therethrough. U.S. Pat. No. 4, 667,093 of McDonald discloses, in addition to the well-known use of an array of photo sensors, an additional photo sensor which is not aligned perpendicularly to the path of travel of the coin through the coin path, but rather is arranged at an angle thereto. In this way, the nominal "diameter" of the coin can be measured as a function of how long it takes to pass by the angled photo sensor. By comparing the thusly computed "diameter" with the diameter measured by the photo sensor array, the thickness of the coin can be deduced.
It has also been known in the art to use magnetic coils to try to evaluate the material of which the coin is made. For example, the following U.S. patents describe the use of magnetic coils for such a purpose: U.S. Pat. Nos. 4,577,744 of Doucet; 5,076,414 of Kimoto; 4,531,625 of Yonekura, et al.; 5,033,603 of Kai, et al.; and, 5,538,123 of Tsuji. Known material sensing apparatus generally disadvantageously employ an associated resonant circuit or tank circuit for operation of the magnetic coils. However, the use of a resonant or tank circuit has the disadvantage of frequency shifts with time and temperature.
Although the prior art shows numerous laudable efforts to provide an effective coin discriminator or coin validator, the prior art generally suffers from being too complicated, not rugged enough, and not jam-resistant enough. The known prior art also tends to have less than optimum accuracy in discriminating coins, rather low dynamic range in terms of the size of the coins that can be discriminated, a limited number of valid coin types can be discriminated, and often has only moderate sensitivity (precision of the measurement). In addition, the known prior art generally has difficulties when a coin or slug has a hole formed therein. Also, the known prior art tends to require high power levels, has difficulty in maintaining field accuracy, and can be difficult to manufacture with a high degree of repeatability. Accordingly, it is to the provision of a coin validator which overcomes these problems of the known prior art to which the present invention is primarily directed.